Brindle is one of the recessive genes on the K locus. There are three K locus genes - K (dominant black, sometimes written as KB), kbr (brindle)
and k (non-solid black - allows A locus to be expressed). K is the top dominant and k is the bottom recessive. kbr sits between the two.
It is entirely dominated by K (so just one K allele will stop brindle from being expressed), but is dominant over k, so a brindle dog can have the genotype
kbrkbr or kbrk.

A dog with one or two kbr alleles will express whichever alleles it has on the A locus, but any and all phaeomelanin (red) in the coat will be brindled. This means that
the extent of the brindling on the coat depends on the A locus. The following list shows how the different A locus genes affect the appearance of brindle.

Brindle + AyAy (sable) - dog will be solid brindle (possibly with darker areas on the back and head where the tipping
on the sable would be)

Brindle + awaw (agouti/wolf grey) - effect on dog is unknown. Would most likely appear to have brindle points, or brindle may
not appear at all

Brindle + aa (recessive black) - dog will be solid black, liver, blue or isabella (recessive black does not allow the production of phaeomelanin in the coat)

Brindle typically appears as black stripes on a red base. The stripes are eumelanin and the base is phaeomelanin, so the appearance of those pigments
can be changed by any of the genes which usually affect them.
- Eumelanin (the pigment making up the stripes) can be affected by: merle (and harlequin), liver, dilution, greying, and recessive red.
- Phaeomelanin (the pigment making up the base) can be affected by: Intensity locus.
And of course, white markings and ticking can occur on any brindle dog.

Recent research into brindle has caused a stir by apparently showing some brindles are genetically dominant black, prompting theories regarding other possible genes or modifiers that may be responsible for the pattern in some breeds. However, brindle is notoriously difficult to detect through testing and there are currently no commercially-available tests for the allele. Most brindles test as k (non-black) through standard tests, however slight variation in the allele between breeds could account for it sometimes testing as K (dominant black), as per the study. As the testing method used was not able to detect brindle at all, the results are not as significant as they at first appear.

Variations in Striping

Stripe width can vary greatly, and it is not known which genes, if any, are responsible for this variation.

These two Greyhounds represent a typical "light" brindle and a typical "heavy" brindle. A brindle is light when the overall appearance is of a red dog
and heavy when the overall appearance is of a black dog, although terminology can vary across breeds.

This Staffie shows even heavier black striping than the Greyhound above. There is only a very small bit of tan visible on the hip, and the rest of the
dog appears solid black. This type of striping is sometimes called "black brindle" or
"reverse brindle".

Variations in Base Colour

The base colour on a brindle can vary as much as red can usually vary, from a deep Irish Setter colour to a light cream. A light
base coat on a brindle is generally due to the Intensity locus, which dilutes phaeomelanin (red
pigment) to cream, but has no effect on eumelanin (black pigment).

These are all details taken from photographs of brindles with black stripes.

Brindle with a Mask

A dog that has at least one Em allele on its E locus will have a black mask. This is an area of eumelanin covering
the muzzle and sometimes the ears. If a dog is a brindled sable (brindle gene + sable gene), it'll be brindle all over, and on dogs like this masks may be visible.

You may notice that on the Great Dane above the phaeomelanin (red) is deeper on the back
and on the chest and legs is almost white. This is most likely due to the urajiro pattern (see the C and I locus page). As urajiro only affects phaeomelanin, the black stripes are unaffected. However, the light base colour can make the stripes seem greyish (see below).

Silver Brindle

Sometimes a brindle dog with black pigment may have what appear to be silver stripes, usually on a cream background (never deep red). This colouration
is generally associated with sighthounds, particularly Afghan Hounds and Borzoi. The overall effect may be similar to how a blue brindle (dd dilution gene) would look.
Silver brindle is caused by the greying gene (G locus), which turns black to grey as the dog ages.
Sometimes dogs with black stripes and a very light cream base (see above) are also referred to as silver brindles. This is because the pale base can cause the black stripes to appear lighter than they actually are. This is often seen in Japanese Akitas, for example.

Brindle and Long Fur

Long, wirey and curly fur can obscure brindle markings by making the stripes less distinct.

Even between longhaired breeds, the visibility of brindle can vary. The Dachshund here has very distinct stripes and is obviously a brindle, but
the Skye Terrier just appears to be a muddy grey/brown. The main way we can tell this Skye is brindled is simply its muddy-coloured coat - this shade
occurs almost exclusively on brindles and not on normal solid reds or sables. It also appears to have some lighter and darker areas, which also suggest it
is a brindle.

This Glen of Imaal's brindling is very obvious on the short fur on its body, but less obvious on the longer fur on its head. If the Skye above were to be shaved down, it would look something like this. The brindling is still present as normal at skin level, but becomes obscured by long coats.

These Wolfhounds and Deerhound show brindling on wirey coats. On the first two dogs, greying has caused the black striping to fade out.

Brindle Tan Points and Saddle Markings

Because the brindle gene allows expression of the A locus, any A locus coat patterns can show brindling on their red sections. The main patterns
are sable (AyAy) and tan points (atat). A sable brindle will
appear solid brindle (in fact, all solid brindles are sables), although any areas of shading will remain dark. A tan pointed dog with the brindle gene will appear black/liver/blue/isabella with brindle points instead of tan.

All of these dogs display black-pigmented dogs with brindled points, with or without white markings.

Crossbreed photo by (unknown)These two dogs are brindle with saddle markings(atat plus an unknown modifier, see the Agouti page). Note the large areas of solid black on the back and brindled tan
on the legs and head. The Cardigan Welsh Corgi also shows white in the irish spotting pattern.

Brindle Saluki puppy photo submitted by Tara Meikle

There is one apparent exception to the rule that only the tan areas on a dog show brindle striping. Dogs with the Eg (grizzle/domino) allele seem to show brindle mostly on their darker areas or saddles, as the Saluki puppy above shows. These dogs look very similar to a saddle tan or shaded sable, but the pattern is caused by a different mechanism. See the E series page for more information on grizzles and how Eg interacts with brindle. It is possible that the Eh allele (which causes a similar pattern in Cocker Spaniels) interacts with brindle in a similar way too.

Brindle Merles

A brindle with stripes that appear to be broken up into shorter stripes and spots may be a merle. As with the Staffordshire Bull Terrier cross shown above (submitted by Ally Stern), the effect can be very subtle. Brindle merles are dealt with on the merle page.

Liver and Dilute Brindles

A brindle dog will have liver (brown) stripes if it is bb on the B locus, blue stripes if it is dd on the D locus,
and isabella stripes if it is both dd and bb. Dilution affects phaeomelanin (red) too to some extent, so the base colour
will be relatively light (certainly not a deep red colour, but more likely cream).

The first two photos show Ambrose, owned by Julie, and the third photo was kindly submitted by Abby L

Liver brindles. Liver and brindle do not occur together on many breeds, however the combination is fairly common in Pit Bull types.

Here are three blue brindles. The Whippet is a very light brindle, and the blue colouration is mostly visible on the mask and nose.
The Neapolitan Mastiff, on the other hand, is a heavy brindle, so the overall appearance is blue.

When the liver and dilution genes are combined, the result is isabella (lilac). Isabella brindles are extremely difficult to distinguish from a solid isabella as the stripes and the base coat are such a similar colour. Neapolitan Mastiffs are one of the few breeds where dilution, liver and brindle all occur together.

"Missing" Stripes

On some light brindles there may be solid red areas where it appears stripes are "missing". This is particularly common in Whippets,
but the genetic basis is unknown. Have a look at the Whippet below. In the first picture the brindle appears normal, however in the second picture you
can see a large clear area on the dog's side.

Sophie, submitted by Helen Lottridge

The stunning mixed breed above appears to have some missing stripes on the inside of her front leg.

Quick Summary!No time to read the whole thing? Here's the quick version!

Brindle (kbr) is in the middle of the K locus, recessive to K but dominant over k. If a dog is kbrkbr or kbrk then it will display its A locus genes, just like a kk dog, but any phaeomelanin (red/tan) in the coat will be brindled.

The dark (eumelanin) stripes on a brindle can be affected by liver, dilution, greying or merle, and the light/red (phaeomelanin) stripes can be affected by the Intensity locus. The thickness of the stripes can vary, so the dog may look predominantly dark or predominantly red.

Dogs with the Eg gene (Salukis, Borzoi, Afghan Hounds) are affected differently by brindle, with the brindling appearing mostly on the dark (eumelanin) areas of the dog. This accounts for examples of dogs that appear to have brindled saddles but no brindling on the legs.

Further Info and Links

Brindle in dogs is located on the K locus, which is CBD103 (Canine Beta Defensin 103). It is an unstable allele that causes some cells in the body to act as K (dominant black) and some to act as k (non-black), in a similar way to a chimaera (fusion of two embryos) or to a tortoiseshell cat (X-chromosome inactivation). In fact, in horses there is no gene for brindle, and when brindle occurs it is always indicative of a chimaera. Brindle dogs are not chimaeras, however, but they are mosaics, which is when different cells in the body become genetically distinct during development. There are many different types of mosaics, but tortoiseshell cats are one type (X-chromosome inactivation means that some cells switch off the black allele and some switch off the red allele - see the "Notes on Mutation etc" page for a full explanation). Interestingly, a form of mosaicism in humans results in a brindle-like pattern known as Blaschko lines.

Because a brindle dog will have some cells expressing k and some expressing K, this makes testing for brindle extremely difficult. There are currently no commercial tests available for the kbr allele, but the allele has been identified by at least one laboratory. In commercial testing, all brindles will test as either k or K.

Apart from horses and dogs, one of the only other species that appears to have a similar brindle pattern is domestic cattle, like the bull above. The gene causing brindle in cattle has not yet been located, but as it is common and inherited it can't be caused by chimaerism, as in horses, and cattle are not known to have any BD103 colour genes, so the mechanism must be different to brindle in dogs.

The "harlequin" pattern in rabbits, as shown by Wasabi here (submitted by Beth), can look similar to brindle in dogs. The mechanism does seem to be fairly similar, with some areas of the coat unable to produce eumelanin and some unable to produce phaeomelanin. This could be potentially viewed as somewhere inbetween tortoiseshell in cats and dog brindle, as the effect on more heavily marked rabbits is of large stripe-like patches.

** Please note that I am not a research scientist, and the information on this page comes from my own knowledge and observation of dogs, observational and testing data provided via e-mail by site visitors, any research papers linked on the page, and the information provided by Dr Sheila M. Schmutz on her excellent website http://homepage.usask.ca/~schmutz/dogcolors.html